This application proposes a project site in Pune, India, as a clinical trials unit to join the HIV Prevention Trials Network (HPTN) with the following four specific aims: 1. To conduct multiple Phase I, II and m clinical trials of interventions designed to prevent HIV infection. 2. To identity and address social, behavioral and logistical barriers to screening, enrollment and retention of participants for clinical trials to prevent HIV infection. 3. To identity additional potential cohorts for HPTN trials in India. 4. To participate in collaborative studies within the HPTN to facilitate the development, design and implementation of strategies to prevent "IV infection. This collaborative proposal including investigators at the National AIDS Research Institute (NARI) in Pune, India and the Johns Hopkins University (JHU) has been proposed for the following reasons: A) The success of a 7-year HIV research collaboration between NAM and JHU B) An established and experienced, local Ethical Review Board and Community Advisory Board C) Completion of three Phase I clinical trials, in cohorts of individuals at both high and low risk for HIV, including two multi-national collaborative HIVNET clinical trials. D) Follow-up rates of greater than 92%for three recent HIV clinical trials and 2 prospective cohort studies of individuals at both high- and low-risk for HIV infection. E) An established cohort of more than 2500 high-risk male and female individuals with an annual HIV incidence of 6.4%/100 person years. We have demonstrated the ability to identity, enroll and follow low-risk women, high-risk men, female sex workers, married women at risk for HIV and discordant couples, appropriate for multiple Phase I, II and III HIV prevention clinical trials. Our site is capable of undertaking clinical trials of a variety of potential HIV prevention interventions, including microbicides, barrier methods, behavioral interventions, STD control and post-exposure prophylaxis. We will also apply novel approaches for estimating HIV incidence in other targeted populations for potential HPTU expansion in Pune. We will also undertake a comprehensive behavioral science research agenda to increase community HIV prevention education, to assess the willingness of our populations to participate in HPTN trials, and to ensure adequate the follow-up and retention for HPTN trials. In light of many years of productive collaboration and our prior experience with multinational collaborative clinical trials of HIV prevention strategies, we believe our project site in Pune, India is uniquely experienced and qualified to participate in the HPTN.